Nate Silver has done an overview estimate in the New York Times of last Saturday's turnouts. The Geography of Occupying Wall Street (And Everywhere Else)
Over all, about 38,000 protesters — more than half of the documented total — turned out in the Western Census Bureau Region, which accounts for about 23 percent of the country’s population. On a per-capita basis, the West drew about two-and-a-half times more protesters than the Northeast, four times more than the Midwest, and five times more than the South. And it wasn’t necessarily in large cities — although places like Los Angeles and Seattle had large crowds, so did the wine-and-cheese town of Santa Rosa, Calif., and the college town of Eugene, Ore., among others.
The article has more comparisons to other protest events.
Here is the US breakdown of his estimates.
Some of you may suspect that my reasons for posting do not rise entirely from dispassionate analysis. :)